MEDICINAL cannabis can be legally prescribed for chemotherapy-induced nausea and vomiting (CINV), but few doctors do so because high-quality clinical trial evidence, demonstrating efficacy and safety is lacking, according to authors of a Perspective published online today by the Medical Journal of Australia.

Recent legislation allows the prescription of medicinal cannabis by medical practitioners in Australia for the prevention and management of CINV. Yet in a review of international and national clinical practice guidelines, the authors of the Perspective found there is insufficient evidence to recommend medical cannabis or specific cannabis-based products in the prevention of CINV. As of July 2018, only 34 Australian doctors have taken up the offer to become registered prescribers of medicinal cannabis.

Dr Antony Mersiades, a Clinical Trials Fellow at the National Health and Medical Research Council Clinical Trials Centre at the University of Sydney, and his coauthors wrote that the dilemma illustrates “the challenges of managing community demand for access to such products, and highlight the importance of conducting appropriately designed clinical trials”.

Previous trials of cannabinoid products containing tetrahydrocannabidiol (THC), cannabidiol (CBD) or synthetic derivatives have been compromised by small sample sizes and outdated control arms, Mersiades and colleagues wrote. One in particular was reported to show “a promising efficacy signal and tolerable psychological adverse event profile” despite the fact that one of the seven patients who received the active drug withdrew due to “transient psychotic symptoms”.

“The Therapeutics Goods Administration guidance documents conclude that use of medicinal cannabis for CINV is experimental, and should only be considered for the management of intractable symptoms where standard therapies are ineffective,” they wrote.

A clinical trial is currently underway in NSW to determine the efficacy, safety and cost-effectiveness of using medicinal cannabis to prevent CINV. The CannabisCINV trial is being conducted by the University of Sydney, the Chris O’Brien Lifehouse and other leading NSW cancer centres, and is funded by NSW Health. The trial has recruited over 60 of 80 planned participants for its phase 2 trial, with expansion to a 250-participant phase 3 trial planned if phase 2 results are encouraging.

“The results of such clinical trials will provide guidance to clinicians regarding appropriate use in specific indications, product selection, dosage and titration, and appropriate monitoring of both efficacy and safety,” Mersiades and colleagues concluded.

Cate Swannell

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